My invention is a musical instrument based on the traditional African drum known as a "Dondo". This type of variable pitch drum is often referred to in the United States as a "talking drum", because of the ability to alter its tonal pitch rapidly.
The Dondo has an hourglass-shaped wooden body carved from a wooden log. Circles of goat or lizard skin are stretched over each end and form the vibrating surfaces, or heads, of the drum. Leather or rope lacing is threaded through holes in the edges of the skins, back and forth from one skin to the other, to draw the skins uniformly over the ends of the drum body and tension them. The lacing is continued, around the drum body until the starting end of the lacing can be tied to the other end. To play the drum, it is placed between its player's arm and body, with the arm holding it near the center of the drum body. By pressing the arm toward the body, the lacing is squeezed toward the central, narrowest part of the drum body. This increases the tension of the lacing on the drumheads. The drum is beaten, typically, with a stick in one hand, and with the other bare hand. Squeezing the drum between arm and body changes the drum-head tension, and hence the drum's pitch. This creates the wide and interesting range of sounds which gives this class of drum the nickname "talking drum. "
There are some major problems with the "Dondo", when used by contemporary professional drummers or percussionists.
Environmental factors, principally humidity and temperature acting on the animal skins and leather or rope, directly effect tension in the drum heads. The results are sound quality changes and changes in the drum's response to its player's actions. This creates artistic problems for the musician.
Animal-skin drumheads are easily broken. Because of the continuous nature of the lacing, proper replacement requires removal of both drum heads, and complete replacement of the lacing. The repair operation can require a day's time.
Since it is intended to be held under the player's arm, such a drum is limited to relatively small overall size and modest weights, consequently to a relatively high range of pitch. Because the little drum must be carefully held and squeezed, it renders difficult the effective playing of other types of drums and percussion instruments.
Earlier U.S. Patents in variable pitch drum art have emphasized low cost drums related to the Dondo pattern. Craig Woodson, in U.S. Pat. No. 4,077,297, describes a Variable Pitch Drum which is laced by a "cord" in the same zigzag pattern marking the Dondo design, and altered in pitch in the same manner, "by manually squeezing the cord toward the drum shell, which in that case is a cardboard tube.
U.S. Pat. No. 2,204,987, issued to W. Gussak, describes an instrument with body narrowed at its center. The Gussak patent is limited to the original manner of operation, discloses a "hoop member" for supporting the skin. The specification (p. 1, col. 2, lines 30-36) mentions, but does not appear to further describe, a proposal ". . . to tension the drum heads by means of a foot pedal and spring arrangement." Gussak discounts that possibility, indicating that "such an arrangement does not give the player the "feel of the instrument to enable him to produce the great variety of tones that can be produced by the instant invention."
A later patent issued to the same inventor (U.S. Pat. No. 3,185,013) added a pair of spring-mounted concave pads on each side of the drum at its center whose purpose is to aid in gripping the drum. These additional elements do not control lacing tension and pitch.
Gussak's object (p. 1, lines 20-24) was a small and cheap instrument, and large drums using this tuning principle, nor did his invention incorporate means to overcome the temperature and humidity variability of the original instrument.